"The general public is hereby informed that the government of the Gambia has left the Commonwealth of Nations with immediate effect," it said in a statement. (Agencies)
"(The) government has withdrawn its membership of the British Commonwealth and decided that the Gambia will never be a member of any neo-colonial institution and will never be a party to any institution that represents an extension of colonialism."
The Commonwealth bloc is a voluntary association of more than 50 countries, many of them former territories of the British empire. No government officials could be reached for comment late on Wednesday.
But a foreign ministry official, speaking on condition of anonymity, said that the decision came after the government rejected a proposal by the Commonwealth last year to create commissions in Banjul to protect human rights, media rights and fight against corruption.
The proposal followed an April 2012 visit to the Gambia by Commonwealth secretary-general Kamalesh Sharma, during which he met with President Yahya Jammeh and other top government officials.
Jammeh, who is regularly accused of rights abuses, has ruled mainland Africa's smallest country with an aura of mysticism and an iron fist since seizing power in 1994.
Earlier this year, the Gambia was singled out for its poor rights record in Britain's annual Human Rights and Democracy Report, which cited cases of unlawful detentions, illegal closures of newspapers and radio stations and discrimination against minority groups.
The Gambia is a tiny sliver of land wedged into Senegal. It suffers from widespread poverty but its miles of palm-fringed beaches are a favourite among sun-seeking European tourists.
"The general public is hereby informed that the government of the Gambia has left the Commonwealth of Nations with immediate effect," it said in a statement.